O que essas opções significam exatamente no comando ifup no Linux?

Question

Por favor, alguém pode me explicar mais (talvez com exemplos) sobre as seguintes opções no comando ifup no Linux.

Isso é o que eu encontrei na internet, mas sem mais detalhes sobre isso:

• --force Force configuration or deconfiguration of the interface.
• --allow=CLASS Only allow interfaces listed in an allow-CLASS line in /etc/network/interfaces to be acted upon.
• -X PATTERN, --exclude=PATTERN Exclude interfaces from the list of interfaces to operate on by the PATTERN. PATTERN uses a usual shell glob syntax. If shell wildcards are not used, it must match the exact interface name. This option may be specified multiple times resulting in more than one pattern being excluded.
• -o OPTION=VALUE Set OPTION to VALUE as though it were in /etc/network/interfaces.
• -n, --no-act Don't configure any interfaces or run any "up" or "down" commands.
• --no-mappings Don't run any mappings. See interfaces for more information about the mapping feature.
• --no-scripts Don't run any scripts under /etc/network/if-*.d/
• -l, --list For ifquery, list all the interfaces which match the specified class. If no class specified, prints all the interfaces listed as auto.

Estou usando o Centos 6 e não consegui encontrar o arquivo /etc/network/interfaces , talvez porque eu esteja usando o Network Manger e não as configurações de IP estático.